In many test and evaluation applications it is necessary to control the application and/or interruption of one or more AC and DC sources to a load under test. Moreover, it is often the case that the amount of current consumed by a load should be monitored. Performing both of these tasks has typically required the use of separate and distinct interconnect and monitor components, such as a solid state AC switch or relay for controlling AC current, another type of switch controlling DC current, and additional circuitry used to monitor current flowing through the switch and the load.
In addition to these power supply and current monitoring functions, there is a need to prevent DC current from flowing backward through the switch when the switch is turned off. A further issue is the control current that turns on the solid-state switch, and the desire to provide a visual indication of the state of the switch, with the state of the switch being capable of being monitored from either its control or load side. Unfortunately, present day solid state switches have sufficient leakage current on the load side that can erroneously turn on a neon indicator, even through the switch has been turned off.